Chronic administration of Tribulus terrestris Linn. Extract improves cardiac function and attenuates myocardial infarction in rats

The present study was undertaken to evaluate the cardioprotective potential of hydro-alcoholic extract of Tribulus terrestris Linn. (Family; Zygophyllaceae), a traditional medicine used in Indian and Chinese systems of medicine. Wistar male albino rats weighing 150-200 g were randomly divided into three main experimental groups; sham (saline treated only), isoproterenol (ISP) control (saline and ISP) and Tribulus terrestris treatment groups (T. terrestris and ISP). Saline or T. terrestris extract 250 mg kg^-1 once daily were orally administered for 30 days. Isoproterenol was administered in rats to induce myocardial infarction. On days 29 and 30, the animals of ISP control and T. terrestris treatment group were administered ISP (85 mg kg^-1, subcutaneously) at an interval of 24 h. On the day 31, 48 h after first dose of ISP, hemodynamic parameters were recorded. After sacrificing the animals the hearts were excised and subjected to biochemical, histopathological and ultrastructural studies. ISP-administration produced a significant decrease in the activities of endogenous antioxidant defence enzymes viz. superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSHPx) and tissue antioxidant, reduced glutathione (GSH) along with a concomitant increase in the lipid peroxidation product malonaldehyde (MDA). In addition, a significant decrease in the activities of myocardial injury markers i.e., creatine phosphokinase-MB (CK-MB isoenzyme) and lactate dehydrogenase (LDH) was also observed in the heart of ISP control group as compared to sham control. Cardiac dysfunction was observed as a decrease in mean arterial pressure (MAP), heart rate (HR), left ventricular rate of peak positive and negative pressure change (+) and (-) LV dP/dt and elevated left ventricular end diastolic pressure (LVEDP) following ISP administration. These functional alterations were supported by severe modifications in histopathological and ultrastructural assessment. Pretreatment with T. terrestris resulted in the increased activities of SOD, CAT, GSHPx and prevention of depletion of tissue glutathione along with inhibition of lipid peroxidation. In addition treatment with T. terrestris decreased the leakage of CK-MB and LDH enzymes from myocardium, there was a significant improvement in cardiac function as evidenced by correction of MAP, HR, LVEDP and contractility and relaxation. The possible underlying mechanism of the cardioprotective effect of T. terrestris could be due to restoration of endogenous myocardial antioxidant status or free radical scavenging activity along with correction of the altered hemodynamic parameters and preservation of histoarchitectural and ultrastructural alterations.